[Rockter]

SEMjim...

You are right on your second point, as this changes the sail trim and the interaction with the wind, and hence changes the heeling moment.

You are wrong on your first point, as the mainsheet tension is an action:reaction pair within the structure of the boat, and PER SE, changes absolutely nothing but the mainsheet tension. It does not, DOES NOT, change the heel angle of the boat. As long as it does not change the sail trim, its angle is immaterial to boat heel.

The sail trim change that results from that tension, and/or tension angle change will heel the boat.... as every man and the ships' cats will know on this website.... but the angle of the traveller per se, nor its tension per se, do not heel the boat.

Even if you welded the boom to the mast at the goosneck to maintain sail trim (or locked the boom by any method, however absurd) and then took the traveller away, the heel angle will still not change.

The wind cares nothing about how the boom is fixed... as long as it IS fixed. The wind notices only sail geometry and those pretty curves, and from that, decides a heeling moment. The ship fights it with a reactive moment as the ship heels, and they compromise on a heeling angle that balances the two moments.

The traveller is helping to hold the structure together as this happens, but it does not have to be a traveller that does it. Anything that fixes the boom position will do.... well, at least until you want to change sail trim, then you are probably best with a traveller. A welded goosneck will be quite an inconvenience then. I smile.

Rockter.